WARSAW (Reuters) - Poland will allocate an additional 200 billion zlotys ($55 billion) on defense over the next 15 years to modernize its army amid signs of growing aggression from Russia, a deputy defense minister said. Russia's Zapad military exercises next month in Belarus and western Russia, the largest in years, have raised concerns for their lack of transparency, with NATO worried the official number of troops participating might be understated. NATO Secretary-General Jens Stoltenberg will visit Poland on Thursday and Friday to check on deployment of U.S. troops in the east of the country and to meet Polish, Romanian and Turkish government officials. Poland, alarmed by what it sees as Russia's assertiveness on NATO's eastern flank, has lobbied hard for the stationing of NATO troops on its soil, especially since Moscow's annexation of Crimea in 2014. "The government has approved a legislative amendment ... which gives us nearly 200 billion zlotys over the next 15 years," deputy defense minister Tomasz Szatkowski said, adding that this was in line with plans to raise defense spending gradually to reach 2.5 percent of gross domestic product. "This is not a trivial amount," he told Reuters in an interview. The Polish government agreed in June to raise defense spending gradually from 2 pct to 2.5 percent of GDP. This means that annual spending would nearly double to about 80 billion zlotys by 2032.

HARD CHOICES Szatkowski, architect of a new national concept for defense, said that although the ministry would be getting almost all the money needed to implement the strategy, some "hard choices" will have to be made. The plan is to increase the size of the army nearly twofold and revamp the equipment. Nearly two-thirds of equipment dates from the Soviet era when the country was in the Moscow-led Warsaw Pact. The navy, though, will fare less well from modernization. The ministry has canceled the purchase of two classes of surface vessels, including multi-task frigates used to protect other warships. "We cannot afford to expand the transport fleet," Szatkowski said. Higher spending on artillery, engineering or assault helicopters will come at the cost of expanding the airborne forces. Warsaw plans to acquire fifth-generation fighter jets, but Szatkowski said that this would not happen until the second half of the next decade. Szatkowski defended the spending plans which have been criticized as "unrealistic". "Nobody can release from us the obligation of planning and creating a coherent vision and proving there is money for it - something that is happening for the first time on such a scope in the history of Polish defense planning," he said.